Correctional Service Canada
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INFECTIOUS DISEASE SURVEILLANCE
in Canadian Federal Penitentiaries 2005-2006

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Glossary

Active TB disease: A person with LTBI who has progressed to an active disease. People with active TB disease feel sick, with symptoms that depend upon where in the body TB disease develops. Persons with active TB disease of the lungs or vocal cords typically have a prolonged cough (≥3 weeks), fever, night sweats, weight loss, loss of appetite and feeling very tired. The person may also complain of chest pain, coughing blood and a hoarse voice. Most TB disease remains within the lung (pulmonary TB) and about 50% of these people will have relatively high concentrations of TB bacteria in their sputum/phlegm (i.e., ‘smear-positive’). Smear-positive pulmonary TB is considered more infectious than cases with relatively few/no TB bacteria in their sputum/phlegm (i.e., ‘smear negative’). Some people develop TB disease outside the lung (i.e., extra-pulmonary), such as in the lymph nodes or bones; these people are not considered capable of transmitting TB infection to others. Antibiotic treatment for a minimum of 6 months is required to cure active TB disease.

AIDS: Acquired immunodeficiency syndrome. A person with HIV infection who has progressed to active disease.

Converter: Refers to a person with a previously documented negative TST result who now has a positive TST result. For routine screening purposes, if the previous TST result was 5-9mm then an increase of 10mm is required to be considered a converter. For contact screening, an increase of 6mm is required. This means that infection with TB has occurred in the period between the previous TST and the present TST. Converters have a 5% risk of developing active TB disease within the first two years of infection if HIV negative, higher if the person is HIV seropositive. Antibiotic treatment of latent TB infection (LTBI) can reduce the risk of progression to active TB disease.

CSC-IDSS: Correctional Service of Canada Infectious Disease Surveillance System. It is the health surveillance system of CSC for tracking human immunodeficiency virus (HIV), hepatitis B and C, sexually transmitted infections (STIs), and tuberculosis (TB) in federal inmates in CSC institutions. Data from the CSC-IDSS complement the CSC TB tracking system for monitoring TB infections among federal inmates and correctional staff.

Drug resistant TB, Multidrug resistant TB (MDR-TB), Extensively resistant TB (XDR-TB): Occurs when the TB bacteria can grow despite the presence of certain antibiotic(s) commonly used in the treatment of active TB disease. Therefore treatment for active TB disease should always be tailored to the antibiotic susceptibility of the TB bacteria. MDR-TB is defined as resistance to at least isoniazid (INH) and ri fampin (RIF), two of the most effective antibiotics used to treat active TB disease. Extensively drug-resistant TB (XDR-TB) is TB that is resistant to at least the two best first-line drugs, isoniazid and rifampin, plus resistant to second–line drugs including any fluoroquinolone and at least one of three injectables (amikacin, capreomycin and kanamycin). Drug resistant TB is more complicated to treat and treatment takes longer as the alternative antibiotics are usually more expensive, not as effective and have more side effects. Drug resistant TB is not more infectious than regular TB, and adults with an intact immune system have the same lifetime risk (10%) of developing active TB disease if infected with DR-TB as with drug sensitive strains.

General population inmate: For the purpose of CSC surveillance, an offender is considered a general population inmate if he/she has been in CSC custody longer than 6 weeks from the time of sentencing and is housed in a CSC institution.

HAV (Hepatitis A virus): One class of viral agents that causes the clinical disease known as hepatitis. Hepatitis A and B are the only types of viral hepatitis infections for which a vaccine exists.

HBV (Hepatitis B virus): One class of viral agents that causes the clinical disease known as hepatitis. Hepatitis A and B are the only types of viral hepatitis infections for which a vaccine exists.

HCV (Hepatitis C virus): One class of viral agents that causes the clinical disease known as hepatitis. No licensed vaccine exists for hepatitis C.

HCV antibody test: A diagnostic laboratory test used to determine whether a person has been infected with HCV.

HIV: Human Immunodeficiency Virus is the virus that causes the clinical condition called AIDS. A person with HIV, however, does not necessarily have AIDS.

HIV antibody test: A diagnostic laboratory test used to determine whether a person has been infected with HIV.

Incidence: The number of new occurrences of disease within an interval of time.

Initial assessment: Inmates and staff living and working in Canadian federal correctional facilities are offered annual TST testing. To determine an accurate baseline for the interpretation of future tests, the Canadian Tuberculosis Standards recommends that persons who will have regular testing have an initial 2-step TST. This means that all individuals with a negative initial TST result must have a second TST performed 1-3 weeks later (if the first test is positive, then there is no need for the second step of the 2-step TST). For CSC, the decision was made to allow a valid TST if the second TST step was performed within 1 year of the first. The second test will be positive if the person was previously infected with TB but their immune system needed a little more time to mount a full response to the challenge of the TB protein. If the second TST is omitted, it is considered an incomplete 2-step and their baseline TB infection status has not been properly established. If they are positive on their next routine annual screening TST, it is impossible to determine if this represents new TB infection (conversion) or the person needed the second TST to boost the immune system response (booster effect) to a past infection. Adequate baseline data within the correctional facility environment requires a completed and valid 2-step TST.

Latent TB infection (LTBI): A person can become infected with TB when the TB bacterium is inhaled into the body from someone who has infectious TB disease. Most adults with LTBI never go on to develop active TB disease. The TB bacteria become latent - that is, they are alive within the body but the immune system prevents the bacteria from growing or spreading. Changes in the lungs from TB infection can sometimes be seen on chest x-ray. Without treatment, approximately 10% of infected adults may progress to active TB disease at some point during their lifetime, with the risk being greatest (5%) within the first two years after infection. Antibiotic treatment can reduce the risk of subsequently developing active TB disease. People with LTBI do not have any symptoms and cannot transmit the TB bacterium to anyone else.

New admission: A new admission is when there is a new warrant of committal issued. Inmates newly committed to CSC go through 6 weeks of an orientation program.

Normalized Electronic Database: A set of data tables linked by common unique identifiers used in database design to create application efficiencies and limit the size of the database required by limiting the amount of potential empty table space.

Old TB disease: A person with a past history of active TB disease that was either treated or healed spontaneously. The person will have no symptoms of active disease and their TST is usually positive for the rest of their life. They cannot transmit TB infection to others. Their chest x-ray may reveal findings characteristic of past TB disease that may pose a small risk (e.g. calcified apical nodules) or a relatively greater risk (e.g. fibrotic scars) of reactivating into active TB disease in the future. Persons with fibrotic scars on chest x-ray suggestive of old TB and a positive TST should be considered strong candidates for antibiotic treatment of LTBI, regardless of their age.

Ongoing negative assessment: Inmates testing negative on an Initial Assessment, or who have an accepted negative TB status from prior testing, are given an ongoing negative assessment status. This consists of a single TST, a symptom screen, and a risk factor screen. Inmates refusing a TST may be offered a pulmonary x-ray.

Ongoing positive assessment: Inmates testing positive on an initial assessment, or who have an accepted positive TB status from prior testing, are given an ongoing positive assessment status. This involves a symptom check, a risk factor screen, and if warranted, an x-ray and/or referral to a medical specialist.

Positive disease test report: Provides a total of the number of diagnostic tests for a given disease that are positive (new diagnoses) during a specified period of time and reported to CSC Health Services. The number of positive disease test reports reflects those who came forward for testing, were diagnosed with disease, and were reported. It does not, however, represent the total number of individuals living with a disease (i.e., prevalence) or the number of persons newly infected each year (i.e., incidence).

Prevalence: The total number of persons with the disease during a designated time period. Point prevalence is the count of cases at a given time divided by the population at risk. Period prevalence is the number of cases in a given time period (i.e., a year) divided by the number of people at risk during the specified time period.

Risk factor: A behaviour (e.g., having unprotected sex) or characteristic (e.g., age) known to carry a risk of infection for a given disease.

STI: Stands for Sexually Transmitted Infection, which is acquired through sexual contact with an infected person. Currently, CSC conducts surveillance for the three major reported bacterial STIs in Canada: genital chlamydia, gonorrhea and syphilis.

Test positivity: Refers to the proportion of inmates who have been voluntarily tested and among whom a positive disease test was reported.

Testing uptake rate: An estimate of the proportion of inmates who voluntarily test for disease.

Tuberculin Skin Test (TST): A skin test involving the injection of small amount of tuberculin protein under the skin of the forearm. In persons who are infected with TB, the body recognizes this protein which causes the immune system to react. This reaction can be felt as an induration (swelling or bump) at the injection site which is then measured 48-72 hours later. Interpretation of the test depends not only upon the size of the reaction, but also on the possible causes of falsely positive and falsely negative reactions and the person’s risk of progressing to active TB disease if infected. In general, if the induration diameter is ≥5 mm for those who are contacts of known TB disease or HIV-infected but not immune suppressed or ≥10 mm for others, the test is considered to be positive.

Voluntary testing: When a diagnostic test is provided to a patient upon agreement from the individual to be tested. The test is given to elucidate the presence or absence of infection.

Window period: Time period between initial infection and the ability to diagnostically detect an infection. During the window period, antibody testing may show a false negative result, as antibodies have not yet been produced, even though the person is infected.

 

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